In the manufacture and installation of cementitious compositions, two types of mixing are used. Initially, the various ingredients used to form the compositions are combined by dry blending or other dry mixing techniques. Such techniques include the use of mixing equipment having a rotary screw, or blades or baffles rotating in a stationary housing, or those having a rotating or "tumbling" housing with blades or baffles fixed therein. The dry ingredients are thus combined to form a uniformly mixed or homogenous dry composition.
Thereafter, these conventional dry compositions are supplied to a job site in bag or bulk form, and are prepared for installation by mixing with water to hydrate the cementitious components so that the mixture can cure to a solid mass. Cementitious compositions can also be prepared by mixing the individual ingredients, such as cement, sand and some type of aggregate, and an aqueous fluid, such as water, by hand or with some type of mechanical mixer. In any event, the individual ingredients must be thoroughly co-mingled and wet mixed with the proper amount of water to hydrate the dry components so as to provide a final cementitious composition with the requisite integrity for commercial use.
While hand mixing can prove to be a most effective way of attaining a cementitious product of proper composition and integrity, the labor and manpower involved have compelled most workers to resort to automated mixing devices. These devices, however, have the disadvantage of being complex and requiring great expenditures of money to supply the energy required for routine operation. In addition, since these devices usually include grinding, blenders or other types of mixing components, the ordinary wear and tear of these parts minimize the effective longevity of the device. Naturally, the worn-out parts could be replaced, but this would require further expenditures of money and could result in machine shutdown time.
In recognizing the need for a more cost-effective and practical mixing device, U.S. Pat. Nos. 722,782; 1,029,126; 1,047,680; 1,107,237; 1,473,990; and 4,175,867 each disclose a device for mixing concrete wherein the mixing occurs through a combination of gravitational forces, the structural arrangements of the devices and/or the introduction of pressurized or unpressurized water.
Similarly, U.S. Pat. No. 1,920,463 describes a method of manufacturing artificial sandstone wherein all of the mixing is done by spraying under pressure and where the materials are mixed while freely falling from elevated hoppers directly into the molds defining the contour of the finished product; and U.S. Pat. No. 2,138,172 discloses a batching apparatus wherein a combination of gravitational forces and specially designed baffle means contribute to the batching of the individual components.